1. Field of the Invention
The subject invention generally pertains to doors and more specifically to a door guide that provides a door panel with a breakaway feature.
2. Description of Related Art
Industrial doors are often comprised of a fabric curtain or have one or more panels whose vertical movement between an open and closed position is guided by tracks disposed along lateral edges of a doorway. Examples of such doors include, but are not limited to roll-up doors, concertina doors, planar doors and overhead-storing doors.
A roll-up door typically includes a pliable roll-up panel or curtain that is wound about an overhead roller. The curtain often includes several spaced-apart horizontal stays or wind bars that are relatively rigid to help prevent the curtain from billowing when subject to an air pressure differential across opposite faces of the curtain. To close the door, the roller pays out the curtain as two vertical tracks disposed along either side edge of the doorway guide the side edges of the roll-up panel generally along a vertical plane across the doorway. The rotation of the roller is reversed to open the door. Roll-up doors are typically either powered open and closed, or are powered open and allowed to fall closed by gravity.
A concertina door typically includes fabric curtain similar to a roll-up door with vertically spaced horizontal bars disposed thereon. To open and close the door, vertical straps are connected to a roll-tube above the doorway and are also connected to alternating bars disposed along the curtain. Winding up of the straps lifts the bottom bar, which also picks up the bars above, while the curtain fabric folds (concertina-style) between the accumulating bars. When fully open, the bars and folded-up curtain are aggregated above the doorway. Unwinding the straps reverses the process. As with a roll-up door, the vertical movement of the curtain and bars are guided by vertical tracks disposed along each side of the doorway.
A planar door includes a door panel that remains generally planar as the panel moves vertically between its open and closed positions. When open, the door panel stores generally adjacent a wall above the doorway with the plane of the panel being parallel or at a slight angle to the wall. Again, the vertical movement of the door panel is guided by vertical tracks disposed along each side of the doorway.
An overhead-storing door includes a series of panels that are pivotally interconnected at horizontal joints. As the door closes, vertical guides along the lateral edges of the doorway guide the panels to a vertical position. When the door opens, the pivotal joints allow the panels to store horizontally overhead, as in a conventional garage door.
Industrial doors, such as the ones just described, are commonly installed in warehouses where the doors are very susceptible to being struck by forklifts or other vehicles. To protect the door and the vehicle from damage, often some type of breakaway or compliant feature is added to the door, which allows the door to move into and out of the doorway in the event of an impact. Although there are a wide variety of breakaway devices available, perhaps the most economical is one where the vertical guide comprises a flexible strap that yields to release a struck door panel.
For example, a guidance device of the published international patent application WO98/48139 (Oct. 29, 1998) employs a fabric strap as a guide or track for the vertical movement of a door panel (i.e., a curtain with or without horizontal bars, a rigid single panel or panels, etc.). If the panel is struck, the flexibility of the strap allows the panel to break out from within the guide to prevent damaging the panel or the track. Although the guide is flexible for most of its length, its lower anchor is a fixed hexagonal post that protrudes several inches into the doorway. If a forklift or the load it is carrying were to hit the post, it could permanently bend or break off entirely. Thus, the protruding post provides a hard stop that can narrow the effective width of the doorway.
In order to provide a door with a breakaway feature, in one embodiment a door guide is provided with a yieldable strap that is disposed between two anchors, wherein at least one of the anchors is moveable from a normal position to a yielded position in response to an impact. The moveable anchor may be resiliently returnable to the normal position after the impact.
In some embodiments, the lower anchor is biased to its normal position.
In some embodiments, the lower anchor is biased to its normal position by way of a spring.
In some embodiments, the lower anchor is biased to its normal position by way of a torsion bar.
In some embodiments, the lower anchor is biased to its normal position by way of tension in the strap.
In some embodiments, the lower anchor is biased to its normal position by virtue of the lower anchor consisting of a resilient polymer.
In some embodiments, the strap is held in tension by a spring.
In some embodiments, a single strap is disposed along each lateral edge of the doorway, wherein each strap loops underneath a lower anchor to provide two generally parallel strap segments between which a door panel is guided.
In some embodiments, the guide strap is of a color recognized by OSHA (Occupational Safety and Health Administration of the U.S. Department of Labor) as a safety color (e.g., yellow, orange, or red) to serve as a safety warning that identifies the proximity of a hard edge of a doorway.
In some embodiments, the guide strap includes a reflective surface to provide a clearly visible indication of the proximity of a hard edge of a doorway.